Schottky diodes have been used to replace P-N junction diodes in many applications. In particular, Schottky diodes have been used to replace P-N junction diodes in power MOSFETs (i.e., MOSFET with body diode in parallel with source and drain). Power MOSFETs that implement P-N junction diodes exhibit several undesirable characteristics, which include: large forward conduction loss, storage of charge between body-epitaxial junction when operating in forward bias, excess stored minority charges which cause large recovery currents and voltage overshoots when the power MOSFET is switched from forward bias to reverse bias, generation of radio frequency interference during fast switching. All of these characteristics cause unnecessary stress to the device, leading to sub-optimal performance.
Schottky diodes exhibit several desirable characteristics which make it preferable over P-N diodes, particularly in a power MOSFET configuration. The low forward drop of the Schottky diode during forward conduction reduces power dissipation of the device and leads to lower conduction loss. The conduction of the Schottky is carried out by majority carriers, so minority carrier charge storage effects do not occur during switching of the device. As such, the Schottky diode is preferred in power MOSFET configurations.
As applications of power MOSFETs employing Schottky diodes become more widespread, it becomes even more important to improve the device configuration to reduce productions costs. One particular important consideration is the reduction of surface areas on the semiconductor substrate occupied by the Schottky diodes. Reduction of surface-area utilization of Schottky diodes provides a key to reducing the manufacturing costs and further miniaturizing the size and shape of electronic devices to achieve portability and other functional enhancements.
It is within this context that embodiments of the present invention arise.